Synthesis and electrochemical properties of cobalt vanadates vs. lithium

A coprecipitation method has been used to prepare several cobalt-based vana dates. New hydrates such as beta-Co(VO3)(2). 2H(2)O, Co2V2O7. 3.3H(2)O, Co- 3(VO4)(2). 12H(2)O and (NH4)(2)Co2V10O28. 16H(2)O have been obtained. Durin g the synthesis, several parameters, namely the pH value, must be finely co ntrolled to prepare pure phases. Thermal treatment of these: hydrated precu rsors give well-known related anhydrous compounds as well as new ones such as beta-Co(VO3)(2). All these materials were tested for their electrochemic al properties vs, lithium. The best results were obtained for the alpha-Co( VO3)(2) phase that can reversibly react with 9.5 lithium ions with only 17% of irreversible capacity leading to a total reversible capacity of 600 mAh /g after the 5th cycle. (C) 1999 Elsevier Science B.V. All rights reserved.